This depicts that after the withdrawal of the astrophysical system from the equilibrium state, \(\Pi _{(1)(1)}=\Pi _{(2)(2)}\)  is satisfied but the case is not the same for \(\Pi _{(2)(1)}\) . As the system withdraws its equilibrium state, the function \(\tilde{f}\)  administers its evolution. So, \(\tilde{f}\)  cannot be zero which in turn exhibits that \(\Pi _{(2)(1)}\)  should also be non-zero (along with the contribution of dark source term \(\mathcal {T}_{21}\)  absent in Eq.(67) in [1]}) even if it vanishes initially. It is worth-noticing from Eqs.(REF ) and () that the function \(\tilde{f}\)  prompts the dissipation process. For the case of spherical symmetry, such physical quantities are responsible for bringing on anisotropy in pressure when the system leaves its initial state with pressure isotropy in it.
